2004 -- In August, Jobs is diagnosed with pancreatic cancer and undergoes surgery. He recovers and returns to work in September.

2007 -- Jobs announces the iPhone, one of the first smartphones without a keyboard, at Macworld Expo.

2008 -- In late December Apple announces that Jobs will not deliver the keynote at the 2009 Macworld Expo or attend the event, sparking speculation about his health.

2009 -- In early January Jobs says his dramatic weight loss was caused by a hormone imbalance. He says the condition would not hinder his abilities to function as CEO. Around a week later Jobs says he will take a leave of absence from Apple until June because his medical condition had changed. He does not disclose his ailment. COO Tim Cook will handle Apple's day-to-day operations during Jobs' recovery period. Apple says Jobs will be involved with major strategic decisions.

June 2009 -- The Wall Street Journal reports that Jobs underwent a liver transplant. A Tennessee hospital later releases a statement confirming the operation.

June 2009 -- Apple confirms that Jobs is returning to work at the end of the month.

January 2010 -- Apple announces the iPad tablet computer, which becomes an instant success and spawns a new category of mobile computing devices.

September 2010 -- Jobs appears on stage in San Francisco to announce Apple's second-generation Apple TV set-top box, which streams movies from the Internet or mobile devices like the iPhone and iPad directly to TV sets.

January 2011 -- Apple announces Jobs is taking a medical leave of absence, without specifying a reason for the leave or how long he'd be away. Questions are raised about the severity of Jobs' health problems, and its impact on the company's stock, product development and business operations.

March 2011 -- Taking a break from his medical leave, Jobs makes an appearance at an event in San Francisco to introduce the iPad 2.

June 2011 -- While still on leave, Jobs appears at the Worldwide Developers Conference in San Francisco to introduce the iCloud and iOS 5. A few days later, Jobs appears in front of the Cupertino City Council with a proposal to build a spaceship-like campus in the city.

August 2011 -- Jobs steps down as Apple's CEO, saying he can "no longer meet my duties and expectations as Apple's CEO." Chief Operating Officer Tim Cook assumes the CEO title. Jobs remains at Apple as chairman of the board.